1. Field of the Invention
The present invention relates generally to devices and methods for ligating body structures and, more particularly, to devices for positioning a pre-formed ligating loop around the body structure and tightening the loop using a device which can be manipulated with a single hand.
Pre-tied ligating loops are utilized in surgical procedures for a variety of purposes. Most commonly, the ligating loops will be placed around the outside of a severed body lumen, such as a blood vessel or the cystic duct, tightened by pulling on a free end of the ligature, and severed using separate severing shears. Usually, the ligating loop will be mounted on the end of a rod or tube so that the surgeon may hold the knot in place with the tube while pulling on the free end of the ligature to tighten the loop.
One form of a ligating loop applier comprises a hollow tube carrying the ligating loop at its distal end. The free end of the suture is threaded proximally through the lumen of the tube and secured to the proximal end of the tube. A small section of the tube near the proximal end is weakened so that it may be easily broken off by the surgeon. By breaking the proximal end off, and pulling proximally on the suture, the ligating loop at the distal end of the tube may be tightened.
While such ligating loop appliers are commonly employed in surgery, including laparoscopic surgery, they suffer from requiring two hands for use, i.e. a first hand to hold the suture applying tube and a second hand to break off and pull on the proximal end of the tube. Manipulation is further complicated by the need to use a stainless steel tube to protect the loop as it is being introduced through a conventional trocar sleeve of the type used in laparoscopic surgery. Additionally, use of such loop appliers has generally been limited to insertion through conventional 5 mm trocar sleeves which have been pre-positioned at particular locations in the body. The number and size of such trocars should be minimized in order to minimize trauma. It would often be desirable to insert the loop appliers through other locations without the need to position additional trocar sleeves or to withdraw other instruments which are already in place in the existing trocar sleeves.
It would therefore be desirable to provide improved suture applying devices which can be manipulated using a single hand, including both placement of the loop about a target body structure and tightening of the loop using only the single hand. Most desirably, the device could be introduced through a cannula of reduced diameter to minimize trauma.
A useful design for such a "single-handed" ligating loop applier would employ a three-finger actuating assembly, including an actuator which is engaged by the users middle and index fingers and a thumb rest at the proximal end of the device. By attaching the free end of the suture to the actuator, the user could first position a ligating loop held at the distal end of the device at a desired target location and thereafter tighten the loop by translating on the actuator by closing the middle and index finger in opposition to the thumb. Such a design, however, suffers from the drawback that the loop-closing stroke is limited in length so that pre-tied loops of only about 2-3 cm in diameter can be closed.
To overcome such a limitation on loop size, it has been proposed that a post be placed on the puller of the ligature applying device and that the free end of the suture be wrapped about the post with the end tied to a portion of the device which remains stationary relative to the puller. When the puller is drawn proximally, a length of suture equal to twice the length of translation will be drawn in. In this way, larger ligating loops can be closed in a single stroke. An exemplary ligating design of this type is described in U.S. Pat. No. 2,610,631.
While workable and an improvement in many ways over other suture-applying devices, ligators of the type described in the '631 patent suffer from certain disadvantages. First, the ratio of suture uptake to puller travel is limited to a factor of 2. While it would be theoretically possible to wrap the suture around a second post on the ligator body and attach the free end of the puller (thus increasing the ratio to a factor of 3), such additional turns of the suture would increase the chances that the suture would become tangled while the loop applier is in use. Additional turns further compromise the device by increasing the friction between the suture and the posts, thereby reducing the ease of actuation. Moreover, the utility of the device is limited in laparoscopic and endoscopic or other cannula procedures where the applier must be introduced through a trocar sleeve, since the presence of the suture on the exterior of the ligator increases the changes that the suture will become tangled during introduction. Additionally, presence of the coupling mechanism between the puller and the suture on the exterior of the device increases the opportunity for contamination and jamming.
For these reasons, it would be desirable to provide improved devices and methods for applying pre-tied ligating loops to body structures, where the devices and methods are suitable for applying large-diameter ligating loops using a single device in a single hand. Such devices should be of relatively simple construction and should be relatively simple to use. In particular, it would be desirable if the suture be contained completely or almost completely within the interior of the device and that the design reduce the opportunity for the suture to become entangled during use. It would be further desirable to provide systems which permit insertion of the suture through conventional trocar sleeves or other cannulas, where the suture is protected by a sheath which is automatically retracted as the suture is passed through the cannula.
2. Description of the Background Art
U.S. Pat. No. 2,610,631, is described above. U.S. Pat. No. 3,476,115, describes a ligating loop applier comprising a single tube having a frangible proximal end, where the proximal end is attached to a free end of the suture and may be broken off so that a suture loop at the distal end may be drawn closed. U.S. Pat. No. 5,129,912, describes a suture applying device, where a pre-tied suture loop is used for laparoscopic and endoscopic knot tying. Other devices are described in U.S. Pat. Nos. 4,592,355; 3,985,138; 3,665,926; 659,442; U.S.S.R. Patent Publications 1,169,630; 835,429; 552,077; and U.K. Patent 868,634.